I have a dataset and website which is partially derived from Wikipedia text. This seems to be licenced CC BY-SA. (This is merged with other free data: OGL, ODbL, etc).
My dataset is CC BY-SA compatible, and I certainly intend to share it so licensed. Everything downstream of the wikipedia data, dataset-wise will be shared. The sui generis database terms are also fine.
However, I'd like to use some stock photos around the site to jolly it up. I have these under a liberal license which permits sharing, but it's an esoteric, custom license (with exciting, extra terms which I'm happy to comply with, seemingly around me not making tea-towels out of their images). I cannot relicense these images CC BY-SA.
The photos are not really integrated with the data at all: they are illustrative, there to jolly things up. As far as I can tell, Wikipedia itself goes much more than this, and distributes their text alongside illustrations with many licenses which directly add value to the text.
I read the discussions on OpenStreetMap's decision to switch to ODbL, and now facing a similar headache, I can see where they are coming from.
So they clearly think this is fine for them. But when I read the legal code, the definition of "Adapted Material" is broad and vague. It seems to me it would cover such a use case.
Later I might want to do other things tangential to the data. For example, I might want to use a non-free font on the site, or elsewhere on the site host a PDF which is SA incompatible.
What is a good rule of thumb so I can know where the red line is?